Finnish cell phone maker Nokia plans to start a mobile phone service in Japan, probably next spring, with an eye to expanding the market share of its handsets, sources said Nov. 22.

It would be the first time for a handset maker to make inroads into telecommunication services in Japan, the sources said. The move is likely to intensify competition among other domestic cell phone carriers, including NTT DoCoMo Inc., observers said.

According to the sources, Nokia is contemplating starting the mobile phone service in a form called mobile virtual network operator, under which the Finnish manufacturer will use communication lines owned by NTT DoCoMo.

The world's largest cell phone maker will sell high-end handsets in Japan, targeting wealthy consumers, to strengthen its brand image, according to the sources.